2of 18CHICAGO, IL - DECEMBER 08: Dwyane Wade #3 of the Chicago Bulls tries to get off a shot after being fouled by Dewayne Dedmon #3 of the San Antonio Spurs at the United Center on December 8, 2016 in Chicago, Illinois.Photo: Jonathan Daniel, Getty Images

4of 18CHICAGO, IL - DECEMBER 08: Tony Parker #9 of the San Antonio Spurs drives against Rajon Rondo #9 of the Chicago Bulls at the United Center on December 8, 2016 in Chicago, Illinois. The Bulls defeated the Spurs 95-91.Photo: Jonathan Daniel, Getty Images

5of 18CHICAGO, IL - DECEMBER 08: Jimmy Butler #21 of the Chicago Bulls leaps to pass over Patty Mills #8 of the San Antonio Spurs at the United Center on December 8, 2016 in Chicago, Illinois. The Bulls defeated the Spurs 95-91.Photo: Jonathan Daniel, Getty Images

6of 18CHICAGO, IL - DECEMBER 08: Rajon Rondo #9 of the Chicago Bulls puts up a shot between Pau Gasol #16 and David Lee #10 of the San Antonio Spurs at the United Center on December 8, 2016 in Chicago, Illinois. The Bulls defeated the Spurs 95-91.Photo: Jonathan Daniel, Getty Images

7of 18The San Antonio Spurs' Pau Gasol (16) grabs a rebound as the Chicago Bulls' Robin Lopez (8) reaches for the ball in the first quarter at the United Center in Chicago on Thursday, Dec. 8, 2016.Photo: John J. Kim, TNS

8of 18CHICAGO, IL - DECEMBER 08: Dwyane Wade #3 of the Chicago Bulls lays in a shot over Pau Gasol #16 of the San Antonio Spurs at the United Center on December 8, 2016 in Chicago, Illinois. The Bulls defeated the Spurs 95-91.Photo: Jonathan Daniel, Getty Images

9of 18CHICAGO, IL - DECEMBER 08: Cristiano Felicio #6 of the Chicago Bulls dunks over David Lee #10 of the San Antonio Spurs at the United Center on December 8, 2016 in Chicago, Illinois. The Bulls defeated the Spurs 95-91.Photo: Jonathan Daniel, Getty Images

10of 18CHICAGO, IL - DECEMBER 08: Pau Gasol #16 of the San Antonio Spurs looks to pass under pressure from Taj Gibson #22 of the Chicago Bulls at the United Center on December 8, 2016 in Chicago, Illinois. The Bulls defeated the Spurs 95-91.Photo: Jonathan Daniel, Getty Images

11of 18CHICAGO, IL - DECEMBER 08: Jimmy Butler #21 of the Chicago Bulls shoots over Patty Mills #8 of the San Antonio Spurs at the United Center on December 8, 2016 in Chicago, Illinois. The Bulls defeated the Spurs 95-91.Photo: Jonathan Daniel, Getty Images

12of 18CHICAGO, IL - DECEMBER 08: Kawhi Leonard #2 of the San Antonio Spurs dunks over Jimmy Butler #21 of the Chicago Bulls on his way to a game-high 24 points at the United Center on December 8, 2016 in Chicago, Illinois. The Bulls defeated the Spurs 95-91.Photo: Jonathan Daniel, Getty Images

13of 18CHICAGO, IL - DECEMBER 08: Former player Scottie Piipen sits courtside as the Chicago Bulls take on the San Antonio Spurs at the United Center on December 8, 2016 in Chicago, Illinois. The Bulls defeated the Spurs 95-91.Photo: Jonathan Daniel, Getty Images

14of 18CHICAGO, IL - DECEMBER 08: Head coach Fred Hoiberg of the Chicago Bulls questions a referee during a game against the San Antonio Spurs at the United Center on December 8, 2016 in Chicago, Illinois. The Bulls defeated the Spurs 95-91.Photo: Jonathan Daniel, Getty Images

15of 18CHICAGO, IL - DECEMBER 08: Rajon Rondo #9 of the Chicago Bulls moves against Tony Parker #9 of the San Antonio Spurs at the United Center on December 8, 2016 in Chicago, Illinois.Photo: Jonathan Daniel, Getty Images

16of 18CHICAGO, IL - DECEMBER 08: Manu Ginobili #20 of the San Antonio Spurs knocks the ball away from Cristiano Felicio #6 of the Chicago Bulls at the United Center on December 8, 2016 in Chicago, Illinois.Photo: Jonathan Daniel, Getty Images

18of 18CHICAGO, IL - DECEMBER 08: Dwyane Wade #3 of the Chicago Bulls shoots against Dewayne Dedmon #3 of the San Antonio Spurs at the United Center on December 8, 2016 in Chicago, Illinois.Photo: Jonathan Daniel, Getty Images

CHICAGO – Jonathon Simmons would never be more wide open.

He had picked off a pass early in the second quarter of the Spurs’ 95-91 loss at Chicago on Thursday, nothing between him and another highlight-reel dunk but his own imagination.

What happened next typified the kind of night the Spurs endured at the United Center.

“The ball just slipped,” Simmons said.

Yes, Simmons blew a dunk, sure to land him on the national highlight shows for all the wrong reasons.

It was a feeling Simmons said he’d never experienced before.

“How many times have you seen me do that?” Simmons asked rhetorically.

In a vacuum, the Spurs’ loss to the Bulls was just as unforeseen.

It was their first defeat on the road since Tim Duncan retired, their 13-0 start falling one shy of Golden State’s NBA record set last season.

The Spurs, however, saw what happened in Chicago coming. They knew they had been playing with fire.

After falling in double-digit holes in six of the previous seven games – but rallying to win five of those games anyway – the Spurs found themselves down by 18 in the third quarter before getting into the game.

It left coach Gregg Popovich about as disappointed as the coach of an 18-5 team could be.

“Guys get paid a lot of money to be ready to play,” Popovich said. “No Knute Rockne speeches. It’s your job. If you’re a plumber and you don’t do your job, you don’t get any work. I don’t think a plumber needs a pep talk. A doctor botches operations and he’s not a doctor anymore.

The Spurs arrived in Chicago with problems that had been masked by a gaudy record and near record-setting road pace.

Slow starts have become an epidemic since Nov. 25, when the Spurs recovered from a 14-point deficit to win in Boston.

Since then, they had also overcome deficits of 15, 13, 11 and 10 to win games. They also faced a 17-point hole in a Nov. 29 home loss to Orlando.

“I don’t know what’s going on,” said point guard Tony Parker, who returned Thursday after missing a game with a left thigh contusion. “It’s been almost the whole season. I don’t know why we have slow starts.”

Thursday, the Spurs held Chicago to 45 points in the first half. Bulls star Jimmy Butler was scoreless.

And the Bulls led by 13 points.

The Spurs shot 15 of 49 from the floor in the first two quarters. They were 1 for 11 from 3-point range.

The Spurs’ 32-point first half was their worst of the season, supplanting a 35-point first half Monday in Milwaukee that included a nine-point second quarter.

“We go through the motions in the first half,” Popovich said. “Our opponents have outplayed us physically and execution-wise in most first halves for most of the season. We’re not a very consistent team, and we haven’t learned as group the game is 48 minutes.”

With six minutes left in the third quarter, the Bulls led by 18 after two Butler foul shots.

Kawhi Leonard shook of a 3-for-8 first half to finish with 24 points, nearly bringing the Spurs all the way back.

Back-to-back and-1 baskets cut the deficit to six points with 6:09 to go. A 3-pointer from Pau Gasol – who had 13 points and 10 rebounds in his return to Chicago – closed the Spurs within 88-84 with 3:24 to play.

“I think everybody is pretty frustrated,” guard Danny Green said of the Spurs’ slow starts. “Obviously we have to do something to change it. We’ll see what happens.”

One statistic was particularly illuminating in Thursday’s box score. The Spurs attempted only five foul shots Thursday, their fewest since 1999.

The Bulls shot 27, making 21.

Afterward, few players had an explanation for the Spurs’ penchant for starting games in a haze.

Green took a stab.

“It’s taking us a little bit of time to get in rhythm,” Green said. “I think it’s us trying to get used to other teams, instead of doing what we do. I think we’re sitting back and letting them do what they do and feeling them out, instead just playing our game.

“We’re kind of adjusting to them. I think we should take a different approach.”

The solution is as obvious as it is difficult to implement.

“We just have to respond,” Parker said. “Everybody individually, and make sure we play for 48 minutes. Everybody has to do more to make sure we have good starts.”